SRC-456

Solar Power Satellite System Definition Study, Phase I Final Briefing, Volume VII: SPS and Rectenna Systems Analyses, D180-25037-7, NASA-CR-160376, December 1978

Commissioned by NASA Johnson Space Center, contract NAS9-15636. Who paid for a study is recorded because it bears on how its conclusions should be read, not because it makes them wrong.

Published claims resting on this source

• CLM-0977 In 1978 Boeing worked out how the timing reference should fan out across the kilometre-wide transmitter. The choice of how many branching levels to use was tied to how big each controlled patch of antenna could be and how tightly each level had to hold its timing: bigger patches need more levels controlled down to the individual tube, and each level then gets only two degrees of timing error at the reference frequency.
• CLM-0979 The three designs disagreed about what the guide signal from the ground should look like. One used a pair of tones either side of the target frequency; one used exactly the transmitter's own frequency and worried about telling the two apart; and by 1979 the reference design had moved to a coded, spread-out signal, the same family of technique that satellite navigation uses.
• CLM-0981 Smaller patches tolerate more bending: halving the patch from 10 m to 5 m doubles the allowed tilt for the same half-per-cent loss. A separate team found that a metre of bending is close to the limit of what a pointing sensor can tell apart, and that a pointing sensor can use at most three patches while keeping within an arc-minute of error. The tilt limit was set by the Soviet exposure standard at the first grating lobe.
• CLM-0995 The whole ten-kilometre satellite was designed to sway once every fourteen minutes, and the antenna was required to be at least as stiff as once every ten minutes so that ordinary control could keep it pointed to a twentieth of a degree.
• CLM-0998 With the top of a five-kilometre section of the satellite two hundred degrees Fahrenheit hotter than the bottom, the estimate has its free end bending by about eight or about eighty metres during construction. The report's text says eight metres and its own chart says about eighty; the report does not say which is right.

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